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haproxy: restrict specific URLs to specific IP addresses

04-03-2018 | Remy van Elst | Text only version of this article


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This snippet shows you how to use haproxy to restrict certain URLs to certain IP addresses. For example, to make sure your admin interface can only be accessed from your company IP address.

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This example restricts access to the /admin/ and /helpdesk URL's. It only allows access from the IP addresses 20.30.40.50 and 20.30.40.40. Any other IP addresses will get the standard haproxy 403 forbidden error.

ACL for URL's

It uses the acl option. If the requested path begins with either /admin or /helpdesk haproxy sets the restricted_page acl. haproxy also looks at the requesting source IP address. If that matches any of the two IP addresses, it sets the network_allowed acl. If the allowed_network acl is set and the restricted_page is also set, it allows a visitor to go to the page. If the restricted_page acl is set but the allowed_network is not, haproxy will serve a 403 error, thus, disallowing access to that specific URL.

Note that you can use IP addresses but also networks in the src acl. Both 192.168.20.0/24 and 192.168.10.3 work.

frontend example-frontend
  [...]
  acl network_allowed src 20.30.40.50 20.30.40.40
  acl restricted_page path_beg /admin
  acl restricted_page path_beg /helpdesk
  block if restricted_page !network_allowed
  [...]

To use a specific file as error page, use the following config in the defaults section:

defaults
  [...]
  errorfile 400 /etc/haproxy/errors/400.http
  errorfile 403 /etc/haproxy/errors/403.http
  errorfile 408 /etc/haproxy/errors/408.http
  errorfile 500 /etc/haproxy/errors/500.http
  errorfile 502 /etc/haproxy/errors/502.http
  errorfile 503 /etc/haproxy/errors/503.http
  errorfile 504 /etc/haproxy/errors/504.http

The http files are regular HTML files with a HTTP response on top, like so:

  HTTP/1.0 403 Forbidden
  Cache-Control: no-cache
  Connection: close
  Content-Type: text/html
  <!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
  <html><head>
  <title>403 Forbidden</title>
  </head><body>
  <h1>Forbidden</h1>
  <p>You don't have permission to access this area
  on this server.</p>
  <hr>
  <address>Apache/2.4.12 (Ubuntu) Server at example.org Port 443</address>
  </body></html>

This is the default apache error page.

ACL for TCP backends

** update 2017-01-09 **

If you have a non-http service you want to restrict to a few IP's you can use an ACL together with the tcp-request connection reject optio. Here below is a simple example for a MySQL service. Do note that this also works in a frontend block:

listen mysql
      bind            1.2.3.4:3306
      mode            tcp
      acl             network_allowed src 20.30.40.50 8.9.9.0/27
      tcp-request     connection reject if !network_allowed
      server          mysqlvip 10.0.0.30:3306

More info on acl: http://cbonte.github.io/haproxy-dconv/configuration-1.5.html#acl More info on errorfile: http://cbonte.github.io/haproxy-dconv/configuration-1.5.html#errorfile

Password if not from whitelisted network

If you want access to the resource, but are not on the whitelisted network, the recommended way is to setup a VPN. But, if that is not feasable, the below trick allows you to prompt for a password if you're from a different network.

First setup a userlist:

userlist UsersFor_Example
  user user1 insecure-password password1
  user user2 insecure-password password2

This is comparable with your .htpasswd file.

In your frontend, where you have the ACL:

frontend example-frontend
  [...]
  acl network_allowed src 20.30.40.50 20.30.40.40
  acl restricted_page path_beg /admin
  acl restricted_page path_beg /helpdesk
  block if restricted_page !network_allowed
  [...]

Remove the last line (block if) and make the section look like below:

frontend example-frontend
  [...]
  acl network_allowed src 20.30.40.50 20.30.40.40
  acl restricted_page path_beg /admin
  acl restricted_page path_beg /helpdesk
  acl auth_ok http_auth(UsersFor_Example)
  http-request auth if restricted_page !network_allowed !auth_ok
  [...]

If you're on the whitelisted network, you are given access. If you're on a different network, you will be prompted for a password. Make sure you're only using this over an HTTPS protected frontend.


Tags: acl  apache  errors  haproxy  loadbalancer  restrict  snippets  ssl